Controlled absorption refrigeration system



April 24, 1951 J. G. REID, JR 2,550,428

CONTROLLED ABSORPTION REFRIGERATION SYSTEM FiledDed. 18, 1946 2 Sheets-Sheet 1 INVENTOR.

April 24, 1951 J, 3, RE), JR 2,550,428

CONTROLLED ABSORPTION REFRIGERATION SYSTEM Filed Dec. 18, 1946 2 Sheets-Sheet 2 Patented Apr. 24, 1951 CONTROLLED ABSORPTION REFRIGERATION SYSTEM John G. Reid, Jr., Evansville, lnd assignor to Servel, Inc., New York, N. Y., a corporation of Delaware Application December 18, 1946;Ser'ial No. 716,'993

10 Claims. (Cl. '625) a The present invention is fdirectedi'to controls for refrigeration systems and relates "back to my prior'applic'ation Serial No. 586,7-31Jfi1ed Aprily5', 1945, now PatentNo. $502,104, and entitled Refrigeration for all common subject matter.

'While the" present" invention may be used with other refrigeration systems it 'isparticularly adapted "for an absorption refrigeration system of "the type in'which a body of refrigerant is accumulated inianieuaporator'and periodically circulated through a cooling element remote from the evaporator. When heat'is' supplied ata constant rate to such a .systexn'the amount of refrigerant accumulating in the evaporator is 'directly effected by the heat loadron' thesystem so that" with light loads the amount of refrigerant increases and-'at' heavy loads theamountfof refrigerant" decreases. As the amount of refriger ant outio'f solution increases,'the'difiiculty in separating refrigerant from solution increases-With'a resultant loss-of useful heat suppliediforthis 'purpose. An overflow pipe 'may be provided'to limit the amount ofre'frigerant in the evaporator but the overflow of refrigerant from the evaporator also represents 2 a heat: loss inrthe system.

Furthermore, in an absorption refrigeration system of'the' type illustrated in'my pri'orapplication, referred toabove, thegenerator is' heated by steam supplied to a heating chamber vented to the atmosphere to maintain the steam at'atmospheric Epr'essure'and a constant temperature of 212'F. Trinsufficient steam is supplied to completelyfill 'the heating chamber the system will not produce. its maximum refrigerating capacity an'dif'an-excess'amount of steam is -supplied to insure -.complete filling. of the heating chamber a part ofthe steam may escape through the-vent which alsos-constitutes a heatlossin the system.

One of the-objects of the present invention is to vary the'rate of operation of a refrigeration system in'accordance with the-amount of refrigerant: inthe' evaporator ofthe system.

Another object" is to regulate the amount of heatsupplied 'to an absorption refrigeration system in accordance 'w'i'th'the amount ofrefrigerant in the evaporator to. operate the system at varying capacities with the most/economical heat input.

Another object is toiprovidea control for'regulating the amount of heat supplied to an absorption refrigeration system "so ast'o'utili'ze all of the available 'heat supplied from minimum 1 to maximum capacity;

Another object is to provide a'control-forsupplying heat to an absorption refrigeration .system in inverse proportion to the amount of refrigerant in the evaporator to maintain the amount-20frefrigerantoutxof solution within predetermined: limits.

Still another object of the invention is to provide a control for modulating .the amount; of heat supplied to an absorption refrigeration system in response to variations in the liquidlevel of the refrigerant in the evaporator to'vary the amount of heat: supplied in inverse proportion to the amount of refrigerant initheevaporator.

These. and. other objects will becomemore apparent from the following :description' and I drawings in which like reference characters denote like parts throughout-the several; views. It is to be expressly understood, however, that the drawings are for the purpose of illustration onlyand not a. definition of the limits of the invention, reference being had for this-purpose to the appended claims. In the drawings:

Fig. 1 is a diagrammatic viewer an absorption refrigeration" system incorporating the control elements of the .present invention Fig. 2 is a part sectional view of the evaporator and showing the float-operated. controller for varying the electrical resistance of a irhe'ostat in response to variations in the liquid level in the evaporator, and

Fig. 3 is a-diagrammatic view of an electric circuit incorporating" the control of the present invention for regulatingthe-operation of the refrigeration system.

Theabsorption refrigerationsystem illustrated in Fig. 1 ofthedrawings is substantially identical with the-system illustratedand described in the pending application: for 'United States Letters Patent of Albert R. Thomas, Serial 'No. 560,214, filed October 25, 1944, now Patent No. 2,518,202, and entitled Refrigeration. The refrigeration system is ofthe'vacuum type-and utilizes water as a refrigerant and an'aqueous solution of a hygrosopic salt such as lithium bromide as an absorbent. In such a system, liquid refrigerant is introduced into the evaporator m from a condenser H through a U-shaped' tube l2. The evaporator i0 is in the form of a horizontallyarrangedcylindricalidrum and the U-shaped tube [2 has one end connected to a sump l3 at the bottom of the condenser II and its opposite end extended upwardly through the bottom of the evaporator. The refrigerant vapor evaporated 'in the evaporator lllflows to an absorber M where the vapor is absorbed in absorption solution'therein. The absorber M" is also in'the form of a horizontally-arranged cylindrical drum positioned directly below the evaporator Ill. A pipe I extends upwardly from the top of the absorber I4 through the bottom of the evaporator I9 and for a considerable distance above the bottom to provide a stand-pipe therein. The stand-pipe I5 is adapted to exhaust refrigerant vapor from the evaporator II] to the absorber I4 while maintaining a body of liquid refrigerant in the evaporator.

Absorption liquid enriched with refrigerant, or, in other words, a dilute salt solution, i conducted from the absorber I4 to the base of a generator I6 in a path of flow including a conduit II, pump I8, conduits I9 and 26, liquid heat exchanger 2I and conduit 22. The generator I6 comprises a plurality of riser tubes 23 enclosed in an outer shell to provide a heating chamber 24 therebetween. Steam is supplied from any suitable source to the chamber 24 of the generator I6 through a conduit 25. The steam may be supplied under pressure from a metered service line as used in some cities or as exhaust from power or processing equipment or may be generated in a boiler particularly designed for use with the refrigeration system. An outlet vent pipe 26 is connected to the heating chamber 24 of the generator I6 adjacent its upper end to maintain the steam supplied thereto at atmospheric pressure and a constant temperature of 212 F. A condensate drain 21 also is provided adjacent the bottom of the chamber 24.

The heating of the riser tubes 23 by the steam causes refrigerant vapor to be expelled from the absorption solution and such expelled vapor is effective to raise the absorption solution in the tubes by gas or vapor lift action. The expelled vapor passes from the upper ends of the riser tubes 23 into a vapor separator 28 and thence flows through a conduit 29 to the condenser II where the vapor is liquefied. Liquid refrigerant formed in the condenser II flows through the U-shaped tube I2 to the evaporator II], as explained above, to complete the refrigeration cycle.

The raised absorption solutionfrom which refrigerant vapor has been expelled flows by gravity from the top of the generator I6 to the absorber I4 in a path of flow including a conduit 3!], liquid heat exchanger 2I and conduit 3I. The end of the conduit 3I extends into the upper portion of the absorber I4 adjacent the inlet from the stand-pipe I5 and has a plurality of apertures or nozzles therein to provide a distributing pipe 32 for dividing the absorption solution as it is introduced into the absorber to promote absorption of the'refrigerant vapor. The heat liberated by the absorption of refrigerant vapor in absorber I4 is taken up by a cooling medium such as, for example, water which flows upwardly through a bank of vertically-disposed pipes or coils 33 in the absorber. The cooling water may be delivered under pressure into the lower ends of the bank of pipes 33 from a supply main or, as illustrated, may be delivered by an electrically-driven pump unit 34 from a well or cooling tower (not shown). The cooling water is discharged from the upper ends of the bank of pipes 33 in the absorber I4 through a conduit 35. Conduit 35 is connected to the condenser II so that the cooling water also may be utilized to effect cooling in the condenser. The cooling water is discharged from the condenser II through a conduit 36.

- The system is initially evacuated and operates tubes to promote heat transfer.

in a partial vacuum with the generator I6 and condenser II operating at one pressure and the evaporator I0 and absorber I4 operating at a lower pressure. The pressure differential between the high and low pressure sides of the system is maintained by a liquid column in the up-leg of the U-shaped tube I2 between a condenser II and evaporator ID. A similar liquid column is present in the conduit 3| connecting the absorber I4 and liquid heat exchanger 2I. The pump I8 connected between the absorber I4 and liquid heat exchanger 2| also maintains the pressure differential between the absorber and generator I6.

The liquid refrigerant in the evaporator I0 is circulated periodically in an auxiliary loop circuit to adapt the system to refrigerate at a place remote from the evaporator. The loop circuit comprises a conduit 31, electrically-driven pump unit 38, conduit 39, cooling element 40 and conduit 4I. As illustrated in Fig. 1 of the drawings, the end of the conduit 4I extends into the evaporator Ill and has a series of apertures or nozzles to provide a spray pipe 43 for dividing the liquid refrigerant as it is returned to the evaporator to promotev evaporation. Preferably a baffle plate 44 is provided in the evaporator Ill between the end of the liquid distributing pipe 43 and the stand-pipe I5 to prevent the liquid refrigerant from being swept into the stand-pipe with the refrigerant vapor. The cooling element 46 is illustrated diagrammatically as a radiator having vertical tubes extending between upper and lower headers with fins extending across the When the refrigeration system is to be used for air conditioning, the cooling element or radiator 46 extends across a duct 45 and the air in the enclosure to be cooled is circulated over the radiator by a motor-driven fan 46.

The absorption solution in the absorber I4 also is circulated continuously through an auxiliary loop circuit to promote absorption of the refrigerant vapor. The auxiliary loop circuit for the absorption solution comprises the conduit I'I, pump I8 and conduit I9. The upper end of the conduit I'I extends into a sump 56 in the bottom of the absorber I4 and the lower end of the conduit is connected to the inlet'of the pump I8. Conduit I9 is connected at one end to the outlet from the pump I8 and its opposite end extends throughout the length of the absorber I4 adjacent the top thereof. A series of nozzles 5| are provided in the end portion of the conduit I9 extending into the absorber I4 to provide a liquid spray pipe 52 for dividing the absorption liquid into a fine spray as it is delivered to the absorber. During operation of the refrigeration system, part of the circulating absorption solution is diverted from the conduit I9 through the conduit 26 and liquid heat exchanger 2| to the generator I6 as previously described. The control of the present invention limits the amount of refrigerant that can accumulate in the evaporator I!) but an overflow by-pass tube 53 may be provided as a safety device between the evaporator Ill and absorber I4. As thus far described, the refrigeration system is substantially identical with the refrigeration system illustrated in the Thomas application referred to above.

In accordance with th present invention control mechanism is provided for starting and stopping the refrigeration system in response to variations in the ambient temperature of the enclosure to be cooled and regulating the rate of rrtrc'ller A res onsive to. the? liquid. level theevaporatorf F11 455-0011:- hecten to regulate tireoperation of a inotor B for-actuating the dulati-ng valve '6; A"c'ontroller" c responsivef to the: escape: of steam: from tldc heatingchamber '24 of. thege-nerator N5 also is connected to tlie m'otor B and modifies the regulatioh'iby' the controller' Arto :prev'en-t "ovenflowandlwaste of heating. steam at maximum capacity; A-icontroller' ll responsive to'canmpe'n or: closed :pcsition: of the modulating valve 56 startsfor stops the -solutionwpump motor wand cooling-"water lpump'motor 3 1*.

The controllersaAwB, TC- and Dare "suitably connected to actuate the modulating' valve -55: for automatically regulating theoperationrot'the s'yse tem andlas illiistrated inilllig. 3E. they-may beaconnect'ed' inva balanced -electric circuit alike that shown in my epriorapplicatibn Serial No. 586,731 referredito: above: The electric: cirouitis iconnecteds-across the. secondary 5"! of a: s'tep dow-n transformer 58 by conductors "59 and fill. and thermostat' lio is shown diagrammaticallyas an electrfc switch in thercon'diictor 59:for ener orator: l fl is' ti'anslated tomovement of the i contact-63 on the resistance elementtt, A flexible bellows -68 is provided between. the: float: arm 64 andthe 'cas'ing of the'evaporator lento-hermetically=seal the clatter while .pe'rmitting movement of the-fioat arm. A bracket (it: surrounds the floatarm BA inl the "evaporator to: limit its r ange of movement. The arrangement of the controller-: xis-z-preferablvsuch thata relatively small "change in the: liquid. level in? the-evaporarerun will fiioifeflthe contact-arm essfromcneehd to the other ot the resi'stanceelement e2;

The motoi' B is showndiagrammatically in the lowervpart of Fig. -3a 's hacingtwoseparate windlegs" to and 11 fibrrctating an =armature or rotor 1Q incppcsite directions The movable meme-m ter o'f 'the velvet-e its-connected to-the armature shaft; al3 oi thes-motor *Bi by suitable reduction gearin that rotation of the armature inone direction (clcclrwisevwill cause the valve el'ement to o en andirotationoi the armature in the opposite direction counterclockwise) will cause the-valveclement to close. The windingsloaand 1 1' "of the motor 3' are arranged parallel and connectedat? onev end to conductor from the secondary 5! of a transformer 58. An electric'circnitis completed throughieither onelor th'e other of the windings by a tiltin'g'switch contact 15 electrically connected-to theother conductor '59 from theitransformer secondary. The tilting: switch contact lo dependsiirom a U-shaped frame 16 pivotally mounted torock. froma neutral! off position to: one or other. of. itstwo on positions in. contact with motor winding 1-0 or II, respectively. The arms I! and TBNof the 'U-shaped frame 16 are of magnetic material and extend into the i'nagnetic field of a'ipair of relay 'coils' T9 and 80. Aspring "81 is connected to rotate'the shaft 13 to close the valve element '56 when the control. circuit is deen'erg-ized 'but: a' magnetic brake 82" restrains such movement When-the circuit is energized. The magnet coil for the brake 82 may be connected in any suitable Wayand as illustrated in Fig. 3 is connected between the tilting. contact '15 connected to' the conductor 59 'andthe conductor '60. A crank arm 83 on the'motor shaft i3 is'connected-to the movable contact B t-of a follow-up rheostat having a resistance element 85.-

Controller C comprises --a thermal responsive element. 86 located in a well fil in the-steam vent pipe-26 from the heating, chamber 24 0f thegenera'tor l6, seeFig. 1, andatmotor 'or bellows 83 connected to operate the movable-contact 6-9 of a rheostat'having av resistance "element 98, see Fig; 3.

Controller D comprises an electric switch 92 operated by-a cam ll-3 'on the motor shaft 13 and the cam is so arranged'as to close 'the switch immediatelyupon movement of the shaft to open the modulating valve 56 and open the switch upon the last-incrementof movement of the shaft to close the valve.

The relay coils l9" and 89 for actuating the tilting switch are connected inthe opposite sides of the balanced electric. circuit comprising the resistance elements 62: and 953' of the controllers A and C and the resistance element of the follow-up 'rheostat operated by the motor B. Qn'one side'of the balanced "circuitone' end of the resistance element-62 oftheccntroller A is connected to one end of the resistance element Sit-of the controller (3 by a conductor 94; the movable. contact -8'9=of controller-C is: connected to one end of-the relay coil Til-by a con'ductorSB; and the-other end'of. the relay coil is connected to one-end of the-resistance'ilfi of the-follow-up rheostat-by' a, conductor 96.. On the opposite side of thebalanced'electri'c cir'cuit'the opposite end Of the' resistance 62 of the controll'er'ji is connected to one'end of 'therelay coil til 'by'a conductor 91 and the'other end-of the'rel'ay'coil is connectedto-theopposite-candor the resistance 85 of the follow-up rheostat' by a conductor QB. Thesmova'ble contacts 83* and 2 ofthe controller A and follow-up rheostat areconne'cted' to the conductors 5'9 and Gil 'from'the transformer secmilitary 51, respectively.

The refrigera-ntipump motor i 38 and'the mctor of the fanJunit 46 are connected to'h'e energized by a three phas'e power linefll cllf ascontroll'e'd by switches to: and'ltrz; Switches it! and teams operatedinby relay coils ifi3 and flilt a rangcd in 'parallel' iha-reiay circuit" are ccnnectecl acrcss a single phase of the three-phase power line I09. The solution pump motor I9 and cooling water pump motor 34 are also connected to be energized by the three-phase power line I66 as controlled by switches I66 and I61. Switches I66 and I6! are operated by relay coils I68 and I69 in a second relay circuit H including the controller D and a low temperature cut-out switch III responsive to the temperature of the refrigerant in the evaporator I0. The energization of both of the relay circuits I65 and H9 is controlled by a switch H2 which, in turn, is closed by a relay coil II3 connected between the conductor 59 beyond the thermostatic switch 55 and the conductor 66. One embodiment of the invention having now been described in detail the mode of operation is explained as follows.

For purposes of description let it be assumed that the thermostatic switch 55 is closed and movable contacts 63, 84 and 89 of the balanced electric circuit are in the position illustrated in Fig. 3. Such a condition indicates that the ambient in the enclosure to be cooled is above the temperature at which the thermostat 55 is adjusted and that the body of refrigerant R in the evaporator I6 is at an intermediate level between upper'and lower limits. The relay circuit I65 is energized by the switch [I2 and relay H3 so that the refrigerant pump 38 and fan 46 are operating to circulate refrigerant through the radiator 49 and circulate air over the radiator, respectively. The steam valve 56 is partially open so that steam is being supplied to the generator I6. The switch 92 of controller D is closed so that pump I8 is operating to circulate absorption solution in the absorber I4 and the cooling water pump 34 is operating to deliver cooling water to the absorber and condenser II.

The balanced electric circuit is energized from the transformer secondary 51 through the conductor 59 and thermostatic switch 55 to the contact 63 of the controller A and through the conductor 69 to the contact 85 of the follow-up rheostat. As the resistance of the two sides of the balanced circuit are equal the relay coils I9 and 89 produce the same magnetic force on the arms I? and I8 of the U-shaped frame so that the tilting contact 15 is at its neutral position and the motor windings I9 and 'II of the motor B are deenergized. The valve element 56 of the modulating valve 56 is held in its adjusted open position by the magnetic brake 82.

Refrigerant is being expelled from absorption solution in the tubes 23 of the generator I6 at a predetermined rate corresponding to the amount of steam being supplied by the valve 56. The refrigerant vapor is flowing through the conduit 29 into the condenser II where it is being condensed to a liquid and the liquid refrigerant is flowing by gravity through the U-shaped tube 2 to the evaporator I9. As the relatively high temperature air (85 F.) circulates over the surface of the radiator 40, heat is transferred to the relatively low temperature refrigerant (50 F.) in the radiator 40 which appears as sensible heat due to the pressure applied to the refrigerant by the circulating pump 38. The sensible heat in the liquid refrigerant causes part of the refrigerant to evaporate as it is sprayed into the low pressure evaporator I9 from the spray pipe 43. The evaporation of part of the refrigerant reduces the temperature of the unevaporated liquid refrigerant recirculated through the radiator 46.

The refrigerant vapor in the evaporator I6 flows through the stand-pipe l into the absorber I4 and is absorbed in the absorption solution therein. Recirculation of absorption solution in the absorber I4 and the delivery thereto of solution weak in refrigerant from the generator I6 promotes absorption so that a low vapor pressure and refrigerant temperature is maintained in the evaporator I6. Part of the recirculated absorbent is delivered to the generator I6 in a path of flow including the conduit 26, liquid heat exchanger ZI and conduit 22 to complete the refrigerant circuit.

If the heat load decreases so that less refrigerant is evaporated in the evaporator II] the amount of refrigerant in the evaporator will tend to increase. As the amount of refrigerant in the evaporator I0 increases the liquid level will rise and operating through the float 6| will move the contact 63 of the controller A to the left as viewed in Fig. 3 to unbalance the resistance 62 in the electric circuit. With a decrease in the resistance on the left-hand side of the circuit as viewed in Fig. 3 more current will flow through relay coil I9 than will flow through the relay coil 89 causing the contact I5 to be tilted to the left and complete a circuit from the conductor 59 through the motor winding Ill and conductor 60. Energization of motor winding 10 causes the armature 12 to rotate counter-clockwise and operating through the reduction gearing I4 moves the valve element 56 toward closed position to reduce the amount of steam supplied to the enerator I6 and thereby the rate of operation of the refrigeration system. Simultaneously the crank arm 83 on the motor shaft I3 actuates the movable contact 84 of the follow-up rheostat toward the right as viewed in Fig. 3 to again balance the electric circuit after an increment of movement corresponding to the movement of the float 6I so that the tilting contact I5 will move to its neutral position. The magnetic brake 82 produces less resistance than the torque of the motor B when energized so that the motor turns the shaft but produces sufiicient resistance to hold the shaft in any adjusted position.

If the heat load decreases to such an extent as to completely close the modulating valve 56 the cam 93 will open the controller switch D to deenergize the relay circuit I I6, open the switches I96 and I61 and stop the solution pump motor I8 and the cooling water pump motor 34. Also if the refrigerant in the evaporator falls below a predetermined temperature the low temperature cut-out switch II I will open the relay circuit III) to stop the pumps I8 and 34.

If the heat load increases a greater amount of refrigerant will be evaporated in the evaporator I6 and the liquid level will tend to fall. Upon a fall in the liquid level the float 6I of the controller A will move the contact 63 to the right as viewed in Fig. 3. Such movement of the contact 63 will unbalance the circuit on the opposite side so that a greater amount of current will flow through the relay coil 89 than through the relay coil I9 to actuate the tilting switch '55 toward the right. Such movement of the tilting contact 15 will then complete a circuit from the conductor 59 through the motor winding 'II and conductor 66. Upon energization of rhcosta 'to. a a n balance the-circuit. after an increme of; movement correspondin tothe movement of; the float 61,

Within the capaoityiof theunit. the controlv of the present. invention will, maintain the liquid level. and the amountv of refrigerant inithe evaporator within. prcdetermined limits. the con troller A varies theresistance-BZ in: increments proportional to changes in the liquid level in the evaporator, lflyand as the modulating valve 56 will be actuated in amounts proportional to the changes inresistance, the amo nt-of steam supplied to thegenerator willbe variedineinverse proportion. to the amount of refrigerant in the evaporator. Thus, the controlof the present invention limits the maximum amount of: refrigerant outof solutionsoas to maintaintheconr oentration. of the solution within permissible imits, 7

If the heat, load increases. beyond the. capacity of the refrigeration system. the liquid level in the evaporator II! will. continueto fall and the controller A, operating throughthe motor B Will continue to open themodulating valveifi to sup.- p y a maximum amount oi-steamto the heating chamber 24 of. thegenerator I6. Thesystcm will then. operate at. maximum capacity and when steam escapes from. the [heating chamber 2.4 hrough the ventpipe 2t .thecontroller cwill be actuated to. modifythe action of .the controller A and reduce the. amount of. steam. supplied. when any steam escapes thro h th v n p ne 26 the temperature responsive element 8,6 will qu ckly xpandthebellows 88 an m ve the arm 89 of thccontroller C-towa1td the i ht as-v we in File 3 to. d r ase the resi tan e n h l hand side of the alanc d. c r A reat r amount of. curr t will the ho hr ne-l t v relay (101119 to tilt the switch and energize the motor windin 10 and. rotate the motor shaft counter-clockwise to partially close the valve. Thns, the controllers A and C cooperate to supply steam .to the heating chamber 24 to operatethe system at maximum capacity without overflow and waste ofthe heatingsteam.

The control continues 'to operate 1 in the manner described above to vary the amount "of steam supplied to the generator lfi in inverse proportion to the amount of refrigerant in the evaporator It until the ambient to be cooled falls below' a predetermined temperature at which the thermostat 55' is adjusted. The thermostat 55 then opens the electric circuit. Upon 'deenergization of' the electric circuit the switch H2 is opened to. .deenergize the relay circuits 1104 and Hi] 17.0 stop operation of therefrigerant pump motor 38 fan motor -46, solution pump motor I8; and cooling water pump motor .34. Simultaneously the balanced electric circuit and magnetic brake 82 are deenergized and the spring'Bl rotates the vmotor shaft 73 to close the valve 56. During .the last increment of movement of the motor shaft 13 to close the valve element'56' thecam 93 opens theuswitchfiz in the relay circuit H0.

The entire control then remains inoperative until the temperature of the ambient again rises to close the thermostatic switch 55 and energize the electric circuit. Upon energization of the electric circuit the relay circuit 1 051 is energized to start thellefrigerant pump38xand fan motor 36 and the balanced electriocircuit is energized to. render the control operative to supply steam to the generator. When the liquid refrigerant the evaporator I'll falls below apredetermined lever the controller A willinitiate operation of'the from vzero tomaximnm capa ity with. themost economi al use of- .the ava lab e. heat such d motor B. to partially open the alue-.56.. The first movementof. theshait 1. otthe. motor .13

loses the sw t oi the ontrollenDand.their .gizes the relay circuit .LJJJ .to startoperationof he solution-motorpump158 and cooling water Pompeii. Thus, therefri erant pumpmoitor .38 and fanmotor .46. are operatedimmcdia ely upon closin f. the thermostatic switch '55 anethe solution pump motor [Band coolin waterpnmp motor .3 3 are. operated when the. steamvalve .56 op n and st ppe when he steam valve close It will .now be observed that the pres nt in- .ventionprovides a control for varying the rate .of operation of a refrigeration systemin accord nce with he mount f h rieerant ntheevoh orator. It will further beobserved that the nresent.inventionnrovides ac ntrol or egulatin h am unt. of h a u p ed toia absent..- .ti n: r fr eration system to operate he stem inc and stopping. a c cle of. operation. of theoreirigeration. apparatus and. varying the rate-oi operationoi the r irigeration., pparatus dur ng a cy le .of operation. a controller responsiveto a. temperature afieeted. .by .the-evaporator and connected to actuate the control. means for start;- ing and. stoppin op ration of. the cfrig r tion apparatus... ,anda second cont ol r p nsiile to the amount. of refrigerantin. the evaporatoriahd onnected. to actuate the control. meansfor, rogue latine. the. rate; of. operation orthe refrigeration apparatus...

2 In, combination, absorption refrigeration. apparatus including an evaporator, means 01: supplying heat to .the refrigeration ..apparatus ,..a controller .responsiue to a, temperature, .afiectecl by the evaporator for rendering. the hQat..SllD,- plying means'operative and inoperativeto supply heat, to the refrigeration apparatus to, starter op a cy leof operati n... nd asecond controller for: re u t ng. the heatv upply n means, o ary the amountof heat suppliedto the refrigeration apparatu dur nga cyclef oper tion n .resp nsetovariati ns in the amountofre riserant in: the evaporator.

.3. 'In combination,.absorptionrefrigeration.ap

paratus including an evaporator, a, modulatin valve for re ulating the .amount of heat sup.-

h ied to the efri erationapparatus, asc n o er responsive to the temperature ofthemodillm to be cooled for. rendering the modulating valve operative and inoperative .tosupply heattothe r fri eration. app rat o start. and s op. y. 1e of eration. a da second controlle r shonsive tothelevel of reirigerantin ,theevaporator and.

connected to regulate the modulating valve .during acycle of operation to vary theamountoi heat supplied .to .the reirigeration; apparatus .in

inverse proportion tothe am unt. of. refr g ra t in the. vaporator- 4'. In an air cooling system, absorption refrig .eration apparatus comprising a plurality of elements including a generator and evaporator interconnected for the circulation of refrigerant, means for supplying heat to the generator for operating the apparatus to deliver refrigerant to the evaporator, a controller responsive to the amount of refrigerant in the evaporator and connected to regulate the heat supplying means to vary the amount of heat supplied to the generator in inverse proportion to the amount of refrigerant in the evaporator, a fan for circulating air to be cooled over the evaporator, and a second controller responsive to the temperature of the air for rendering the first controller operative to regulate the heat supplying means and initiate operation of the fan.

5. In an absorption refrigeration system comprising a plurality of elements including a generator and evaporator interconnected to circulate refrigerant, said generator having a heating chamber vented to the atmosphere, means for supplying steam to the chamber to heat the generator at a constant temperature, a modulating valve for varying the amount of steam supplied to the heating chamber of the generator, a controller responsive to the liquid level of the refrigerant in the evaporator and connected to actuate the valve to supply steam at a rate inversely proportional to the amount of refrigerant in the evaporator, and a second controller responsive to the temperature of steam escaping through the vent from the generator and connected to actuate the valve to reduce the amount of steam supplied to the heating chamber.

6. In an absorption refrigeration system comprising a plurality of elements including a generator and an evaporator interconnected for the circulation of refrigerant, said generator having a heating chamber, means for supplying steam to the heating chamber of the generator, a modulating valve for regulating the amount of steam supplied to the generator, said evaporator being adapted to maintain a body of liquid refrigerant therein, an auxiliary circuit including a cooling element and pump for recirculating the refrigerant in the evaporator, a float operated controller responsive to the liquid level of the refrigerant in the evaporator and connected to actuate the valve to vary the amount of steam supplied to the heating chamber of the generator in inverse proportion to the amount of refrigerant in the evaporator.

'7. In an absorption refrigeration system comprising a plurality of elements including a gen-- erator, condenser, evaporator and absorber interconnected for the circulation of refrigerant, said generator having a heating chamber, means for supplying steam to the heating chamber of the generator, a modulating valve for regulating the amount of steam supplied to the generator, said evaporator being adapted to maintain a body of liquid refrigerant therein, an auxiliary branch circuit including a cooling element and pump for recirculating the refrigerant in the evaporator, an electric circuit including an electric motor for operating the modulating valve, a controller having a movable element for varying the electric circuit to cause the motor to actuate the valve in proportion to the movement of the element, and a float in the evaporator for actuating the movable element in response to variations in the liquid level of the refrigerant in the evaporator.

8. In an absorption refrigeration system comprising a plurality of elements including a generator and evaporator interconnected for the circulation of refrigerant, said generator having a heating chamber vented to the atmosphere, means for supplying steam to the chamber to heat the generator at a constant temperature, a modulating valve for varying the amount of steam supplied to the heating chamber of the generator, a controller responsive to the temperature of the medium to be cooled for rendering the modulating valve operative and inoperative to control the heating medium, a second controller responsive to the level of refrigerant in the evaporator for operating the modulating valve to supply steam to the heating chamber at a rate inversely proportional to the amount of refrigerant in the evaporator, and a third controller responsive to the temperature of steam escaping through the vent from the generator to modify the regulation of the valve by the second controller to prevent the escape of steam from the heating chamber.

9. In an absorption refrigeration system, a generator, a condenser, an evaporator, an absorber, conduits interconnecting the elements to provide circuits for the circulation of refrigerant and absorbent, an auxiliary circuit including a pump for recirculating refrigerant in the evaporator, an auxiliary circuit including a pump for recirculating absorbent in the absorber, a modulating valve for regulating the amount of heat supplied to the generator, a controller responsive to the temperature of the medium to be cooled for initiating operation of the refrigerant circulating pump and rendering the modulating valve operative to regulate the supply of heating medium, a controller connected to adjust the modulating valve in accordance with the amount of refrigerant in the evaporator, and a controller responsive to the initial opening of the valve for initiating operation of the absorbent circulating pump.

10. In a vacuum type refrigeration system utilizing water as a refrigerant and a salt solution as an absorbent, a plurality of elements including a generator and evaporator interconnected for the circulation of refrigerant, said evaporator being adapted to accumulate a body of refrigerant therein, a cooling element remote from the evaporator, an auxiliary circuit connecting the cooling element and evaporator, a pump in the auxiliary circuit for circulating refrigerant in the evaporator through the cooling element, a modulating valve for regulating the amount of heat supplied to the generator to vary the amount of refrigerant expelled from solution therein, and a float operated controller responsive to the liquid level of the refrigerant in the evaporator and connected to operate the valve to supply heat to the generator at a rate inversely proportional to the amount of refrigerant in the evaporator whereby to maintain the amount of refrigerant out of solution within predetermined limits.

JOHN G. REID, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,414,527 Schurtz May 2, 1922 1,802,516 Keyes Apr. 28, 1931 1,865,349 Wright June 28, 1932 

